1. Field of the Invention
This invention relates generally to improvements in material loading and handling equipment and is specifically directed to a device to selectively prohibit a boom structure from lowering beyond a given height.
2. Description of the Prior Art
Conventional loaders are normally provided with a bucket carrying boom structure that moves up and down adjacent the outer sides of the loader. Generally, the bucket and boom structure is raised and lowered by a hydraulic lift cylinder which is interconnected between the vehicle or a support thereon and the boom structure which is actuated by a control lever in the operator's station.
For certain working situations and for other convenience reasons such as inspection, repair, maintenance, and storage, it is desirable to maintain a bucket and boom structure at a given elevation. Since many of the loaders today employ hydraulics for powering the loader boom, it is desirable to provide a secondary locking mechanism to prevent the boom structure from suddenly lowering due to a failure in the hydraulic system or an accidental movement of the control lever.
The anti-lowering device as set forth in Hurlburt et al. U.S. Pat. No. 3,730,362, issued May 1, 1973 prohibits a boom structure from being lowered beyond a predetermined height by the provision of a pair of cylindrical locking pins disposed adjacent respective sides of a loader for simultaneous longitudinal movement outwardly from the frame, such that the outer portions thereof project into the path of travel of the boom structure. The present invention is an improvement to this device in that it provides for a stop member that prohibits a boom structure from being lowered beyond a predetermined height and in addition permits the boom structure to be raised from below the predetermined height when the stop member is in its locking position.